The present invention relates to a color image electro-photography apparatus and, more particularly to a color laser beam printer.
The color image electro-photography apparatus can provide a color image by applying an electro-photographic technique. The obtained color image of the color image electro-photography apparatus is recorded and reproduced on a recording medium such as a recording paper.
The present invention relates to a color image electro-photography apparatus in which an overlapped toner image comprised of n colors is transferred on a toner supporting body, such n color overlapped toner image can be recorded and reproduced dividedly on a recording medium in accordance with the length of the image.
As a method for recording and reproducing a color image, there is a method disclosed in Japanese Patent Laid-Open No. 83557/1986. In this first color image formation method, the color image formed on a photosensitive drum is transferred to a recording medium which is carried by a transfer drum. The above stated process is carried out repeatedly so as to obtain the necessary number of colors, for example four times for four colors. Accordingly, this color image is reproduced on a sheet of recording paper as the recording medium.
Herein, this first color image formation method, when the size of the obtained color image is A3 size (420 mm in length; 297 mm in width), for example, the color image formation apparatus employs a photosensitive drum having an outer diameter of 80 mm and a transfer drum having an outer diameter of about 160 mm. The peripheral length of the transfer drum is 502.6 mm.
In a color image formation method disclosed in Japanese Patent Laid-Open No. 76766/1985, the toner image having the necessary number of colors, for example four colors, is developed and formed in order on a photosensitive drum, and this color toner image is transferred onto a recording medium at one time. Accordingly, the color image can be obtained on the recording medium.
In this second color image formation method, when the size of the recording medium is A3 size, it is necessary to use a photosensitive drum having an outer diameter of about 160 mm.
In a color image formation method disclosed in Japanese Patent Laid-Open No. 154465/1984, the photosensitive drum, including development apparatus, is prepared with a necessary number of colors, for example two colors. In this third color image formation method, the toner image having a respective color is formed on a respective photosensitive drum, and the color toner image is transferred in order from the photosensitive drum to a sheet of recording paper. Accordingly, the color image can be obtained on the recording paper.
In a color image formation method disclosed in Japanese Utility Model Laid-Open No. 66870/1988, a photosensitive belt member, including developing apparatus, is prepared so as to obtain the necessary number of colors, for example three colors. In this fourth color image formation method, a toner image having a respective color is formed on a respective photosensitive belt member, and the color toner image is transferred in order from the photosensitive belt member to a sheet of recording paper. Accordingly, the color image can be obtained on the recording paper.
There is a further color image formation method disclosed in Japanese Patent Publication No. 30336/1978, by the inventors of the present invention. In this fifth color image formation method, a sheet of photosensitive paper is run so as to obtain the necessary number of colors in a transportation direction X during a development process and in a return direction Y at the finish of the development process. Accordingly, the color image is recorded on the photosensitive paper
To record and reproduce a color image in a color image electro-photography apparatus, there are the following various requirements from the aspect of the manufacturer or the operator.
(a) A requirement to achieve recording and reproduction corresponding to any size (length) of recording medium.
(b) A requirement to achieve the recording of a small (short) record information on a small recording medium in a short time.
(c) A requirement to provide a structure of a small and compact color image electro-photography apparatus.
(d) A requirement to provide a color image electro-photography apparatus having a small number of structural components and a low price.
However, within the above mentioned prior art, in the techniques disclosed in Japanese Patent Laid-Open No. 83557/1986 and Japanese Patent Laid-Open No. 76766/1985, the size of the recording medium is limited due to the outer diameter of the transfer drum and the diameter of the photosensitive drum. Accordingly, the above stated two prior art techniques cannot satisfy the above stated requirement (a).
Further, in the above stated two prior art techniques, the required number of rotations of the transfer drum or the photosensitive drum is constant, and the time required for one rotation of the transfer drum or the photosensitive drum is constant. Therefore, regardless of the size of the recording medium there is no change in the recording time. Accordingly, the above stated two prior art techniques also cannot satisfy the above stated requirement (b).
Further, in the above stated two prior art techniques, making the outer diameter of the photosensitive drum or the outer diameter of the transfer drum large requires that the apparatus be made large, and further it becomes high in cost with regard to a driving source for driving accurately such a large size photosensitive drum or such a large size transfer drum. Accordingly, because of these problems the above stated two prior art techniques cannot satisfy the above stated requirements (c) and (d).
In the prior art techniques disclosed in Japanese Patent Laid-Open No. 154465/1984 and Japanese Utility Model Laid-Open No. 66870/1988, it is possible to satisfy the above stated requirements (a) and (b). However, in these prior art apparatuses, having a large number of the photosensitive drums or a large number of the photosensitive belt members, it is necessary to provide chargers and development apparatuses corresponding in number to the number of photosensitive drums and photosensitive belt members.
Further, it is necessary to maintain accurately the positioning precision between these structural components. Accordingly, the above stated two prior art techniques cannot satisfy the above stated requirements (c) and (d).
In the prior art technique disclosed in Japanese Patent Laid-Open No. 30336/1978, the color image is obtained in accordance with the transportation process and the return-back process of the photosensitive paper. However, it is necessary to have the photosensitive characteristic property in the photosensitive paper itself. Accordingly, in this prior art technique there is no possibility of using conventional paper as the recording medium.